Many arc discharge lamps rely for operation on the presence of mercury in the arc stream. The mercury is present, when the lamp is not operating, as elemental mercury or as a solid or liquid amalgam. In some types of lamps, particularly electrodeless fluorescent lamps such as those shown in U.S. Pat. Nos. 5,717,290 and 5,834,905, it is important to keep the solid or liquid amalgam from settling within the arc environment where it can cause changes in the lumen output and the lumen-temperature performance of the lamp.